This invention concerns a method of palletizing goods such as corrugated fiberboard boxes by one layer and a device therefor, and more particularly the invention concerns a method of palletizing a variety of goods in multiple layers to form a unit load, and a device therefor.
As device handling goods in the unit of layers, there have been known in the prior art those disclosed in Japanese Patent Application Laid Open Nos. Sho 55-111322 and Sho 57-7123, and Utility Model Publication No. Sho 60-19118.
The device disclosed in Japanese Patent Application Laid Open No. Sho 55-111322 comprises a chuck head having a centering mechanism, and a load holding device which is mounted in a position opposite to said chuck head and is advanced/receded from the chuck head by cylinders controlled via positioner.
Japanese Patent Application Laid-Open No. Sho 577123 discloses a device for holding one layer which comprises two pairs of goods pressing devices which are opposed to each other and which can pressingly hold four sides of a layer of goods such as corrugated fiberboard boxes substantially at the same time.
Japanese Utility Model Publication No. Sho 60-19118 discloses a four side clamp lift having four clamp plates which can be rotated so that in a manner allowing at least one of the clamp plates to be moved to a position not to oppose the clamping plates on the other side.
All of the techniques described in the prior art, however, have inherent problems.
In the device of Japanese Patent Application Laid-Open No. Sho 55-111322, as goods are held by linear contact with rollers, this method is hardly effective in holding collapsible cases such as corrugated fiberboard boxes although it is effective in holding rigid articles such as concrete blocks.
The method disclosed in Japanese Utility Model Publication No. Sho 60-19118 can handle a unit load each of which layers comprises corrugated fiberboard boxes and is of the form of a rectangular parallelepiped. However when handling such unit loads after they are transported by vehicles such as a truck, the layers are often disturbed during transportation and clamping plates alone cannot apply sufficient pressure to consolidate the load, and if the pressure should increase, it will damage boxes.
Neither Japanese Patent Application Laid-Open No. Sho 55-111322 nor Japanese Utility Model Publication No. Sho 60-19118 describes nor suggests any means for palletizing a variety of goods in multiple layers.
Japanese Patent Application Laid-Open No. Sho 57-77123 discloses an application of a method for stacking arbitrary goods to form one layer and placing layers on an empty pallet, but it does not disclose a means for controlling the palletizing order. If a layer with a larger area is placed on another layer with a smaller area, the unit load will often collapse during the transportation by a truck.
The above invention also discloses the method applied to a system which palletizes arbitrary goods layer by layer and then on an empty pallet in multi-layers. But as the two pairs of opposing pressing plates are moved to the center in synchronization by respective racks and pinion mechanisms, the centers of palletized layers coincide even if goods of different sizes are assembled in one layer to thereby make all the four sides of the unit load irregular with recesses or projections. Such a unit load should be horizontally strapped across the top most layer to prevent collapses during truck transportation. Utility Model Publication No. Sho 49-41038 discloses one of such strapping devices.
The device which is disclosed in Japanese Utility Model Publication No. Sho 49-41038 is adapted to move an automatic strapping machine forward/backward and the machine needs to be placed at a position substantially close to the goods. This device, if used for the unit loads having unstraight side lines, will not be able to strap them completely. Particularly, if the unit load is shaped like a pyramid, the automatic strapping machine often stays close to the second layer from the top rather than to the topmost layer and thereby fails to consolidate the goods completely.
In the prior art there have been known mechanisms for holding one layer of goods such as the one disclosed Japanese patent Application Laid-Open No. Sho 57-77123; and a positioning mechanism such as the one disclosed in Japanese Patent Publication Sho 50-29230.
In the device disclosed in Japanese Patent Application Laid-Open No. Sho 57-77123, semi-spherical receptors are fixed at four corners of the upper surface of a transportation truck, and rotatable balls are placed upon the receptors in such a manner that a portion thereof projects beyond the rim of the upper surface. The mechanism for holding a layer of goods which is to be carried on the above truck includes a positioning device comprising concave members at the four corners on the bottom surface of a main body of the mechanism with respective centers coinciding with the apexes of said rotatable balls.
Japanese Patent Publication No. Sho 50-29230 discloses a positioning mechanism which moves a floating pallet supported on a fixed frame in a horizontally movable manner together with goods which are placed on the pallet in a substantially random fashion.
The conventional positional mechanisms such as those mentioned above had the following problems. The positioning mechanism described in Japanese Patent Application Laid-Open No. Sho 57-77123 has the structure to position one layer of goods by using rotatable balls and concave members, so that it is not effective when the position of goods deviates widely from the position of the mechanism body. If the scope covered by the centering mechanism is extensive, the concave members had to be made larger in size, which leads to a members greater difference between the center and the periphery of a concave member. If goods with large deviation are attempted to be held with such a mechanism, the holding mechanism will lose horizontal balance and fail to hold goods. Thus merely increasing the size of a concave member did not achieve accurate positioning.
Although the positioning mechanism disclosed in Japanese Patent Publication No. Sho 50-29230 can center goods placed on a floating pallet, it cannot center goods piled in plural layers in the unit of layers. More particularly, if the goods at the topmost layer are held and centered by the mechanism, the goods on the second from the topmost layer or below and the floating pallet will not move and only those at the topmost layer slide and move along upon the layer second from the top. The mechanism is not effective in centering the goods on the second layer and therebelow as they tend to collapse.
Accordingly, an object of this invention is to provide a method for palletizing by layers which can solve these problems encountered in the prior art which can securely hold a unit load which comprises layers of a variety of goods such as corrugated fiberboard boxes, and which can form goods in a predetermined shape in a simple manner and a device therefor.
Another object of this invention is to provide a method for palletizing goods in the unit of layers which can consolidate a unit load of a variety of goods in plural layers in a form suitable to be horizontally strapped by an automatic strapping machine securely and yet easily so as not to cause collapse of loads during transportation and a device therefor.
In order to achieve the above objects, this invention method forms a unit load by assembling a variety of goods for one layer with due consideration to layer area dimensions of such goods, dimensions of void spaces which are not occupied with the goods on the layer, and the dimensional relation among goods, and by stacking such layers from the bottom in the order of the area size of a layer in a manner not to let a package on the upper layer fall into a void on the layer below or not to cause goods project beyond the edge of the layer below to disturb the equilibrium.
The formed unit load is basically in the shape of a pyramid and very stable as there is no possibility for any package to fall downward or project sideward which might otherwise cause collapse of loads.
This invention method is characterized in that it assembles and palletizes a variety of goods layer by layer in plural layers in a manner to make at least one side of the unit of layers of goods form a plane substantially vertical to the bottom thereof.
With such a plane on at least one side of the layer of goods substantially vertical to the bottom surface, the unit load formed according to this invention can be effectively strapped with an automatic strapping machine as the strapper consolidates the boxes by using the plane as a reference and as the side of the assembled boxes form a straight line without irregularities to allow close contact between the strapping machine and boxes.
This invention method is effective in palletizing such slightly loose unit loads as those after transportation by a truck without damaging the goods because the method with two pairs of goods pressing devices presses at least the two sides of a layer of goods of the unit load, then releases the pressure and pressingly holds them again.
The device for palletizing by layer according to this invention includes a mechanism for holding one layer of goods comprising two pairs of goods pressing devices having goods pressing boards and driving mechanisms for the pressing boards which are mounted at four sides to oppose each other, a controller which controls the pressing operation of said goods pressing device, and a controller for the palletizing order.
This apparatus of this invention for holding one layer of goods preferably includes a centering device which comprises ball receptors fixed on a frame (including a truck) on which the mechanism of holding one layer of goods is carried, rotatable balls mounted on the receptors in a manner to partially project therefrom, and flat receiving surfaces on said mechanism to oppose said rotatable balls and which can center said mechanism with the center of goods.
This invention device preferably includes a detector which can detect the position where the truck stops by using a board provided at the advancing end of the truck.
This invention device preferably includes a unit load lifting device which can move unit loads vertically in relation to the mechanism of holding one layer of goods.
This invention device for the palletizing order preferably includes a means to store dimensions of the layer areas of goods, of void spaces unoccupied with goods and of each good so as to select an optional order out of predetermined palletizing orders based on the dimensional relation among the above.
This invention device for the pressing operation preferably includes a means to select a suitable pressure out of plural pressures available.
The effect of this invention device will be achieved as below.
An optimal pressure can be selected from plural pressures operable in the pressing device with said controller so that the layer of goods may be pressed by necessary and sufficient but not excessive pressure determined depending on the particular unit load to achieve effective palletization in the unit of a layer without causing damage to the goods.
The above holding mechanism is made freely movable by said centering device as the main body of the mechanism can slide with the planar receiving surfaces upon the rotatable balls on the frame to be smoothly positioned at the center of goods. Goods in multiple layers may effectively be centered in the unit of layers.
A unit load with at least one side surface thereof substantially vertical to the bottom surface can be easily formed by detecting the pressing board abutted against the advancing end of goods while traveling with said detector to as to align sides of goods in a layer.
Unit loads of a desirable shape and dimension can be formed out of goods piled in an arbitrary height by said unit load lifting device.
Goods are automatically palletized in accordance with the predescribed order of said controller for the palletizing order.
This invention can therefore achieve such effect as palletizing a variety of goods such as corrugated fiberboard boxes in multiple layers to form a unit load securely in a predetermined form in a simple manner. This invention further attains such effect as to allow horizontal consolidation by an automatic strapping machine.